Circuit structure for realizing real-time predistortion calibration of broadband IQ modulation and method thereof

A circuit structure for realizing real-time pre-distortion calibration of broadband in-phase/quadrature-phase (IQ) modulation, wherein the circuit structure comprises:

• a baseband generation module for a calibration signal generator to generate two orthogonal sine cosine calibration signals, respectively, according to a calibration bandwidth and an order of a pre-distortion filter, and a data switch that is switched to a relevant data channel;
• a digital-to-analog conversion module connected to the baseband generation module for converting the signals into analog I and Q baseband signals;
• a detector connected to the digital-to-analog conversion module;
• a frequency synthesis module connected to the IQ modulation module for generating signals in a certain frequency range;
• an IQ modulation module connected to the digital-to-analog conversion module for mixing the analog baseband signal with the local oscillator signal, and summing the output of the two mixers after combining them;
• an amplitude control module connected to the IQ modulation module and the digital-to-analog conversion module for continuous adjustment of a radio-frequency (RF) signal power;
• and
• wherein the digital-to-analog conversion module comprises a digital-to-analog converter and an analog-to-digital converter, the digital-to-analog converter is connected to the data switch, and said analog-to-digital converter is connected to the automatic pre-distortion calibration factor generation unit and the amplitude control module for digitizing the output signal of the detector and generating the frequency response error calibration factor by calculation.

A method for realizing real-time pre-distortion calibration processing of broadband IQ modulation wherein the method comprises:

• (1) providing a circuit structure for realizing real-time pre-distortion calibration of broadband IQ modulation, wherein the circuit structure comprises:
• a baseband generation module for a calibration signal generator to generate two orthogonal sine cosine calibration signals, respectively, according to a calibration bandwidth and an order of a pre-distortion filter, and a data switch that is switched to a relevant data channel;
• a digital-to-analog conversion module connected to the baseband generation module for converting the signals into analog I and Q baseband signals;
• a frequency synthesis module connected to the IQ modulation module for generating signals in a certain frequency range;
• an IQ modulation module connected to the digital-to-analog conversion module for mixing the analog baseband signal with the local oscillator signal, and summing the output of the two mixers after combining them;
• an amplitude control module connected to the IQ modulation module and the digital-to-analog conversion module for continuous adjustment of a radio-frequency (RF) signal power;
• and
• wherein the baseband generation module comprises:
• a baseband generation unit for generating two orthogonal digital I and Q path signals depending on the signal regime or type;
• a pre-distortion filter connected to the baseband generation unit for pre-distortion of the baseband signal that is loaded in real time with an automatically generated h-factor;
• an automatic pre-distortion calibration factor generation unit for processing collected frequency response data, generating a pre-distortion calibration factor, and converting this calibration factor into the h-factor for the pre-distortion filter;
• a calibration signal generator for generating a digital baseband calibration signal, and two sine and cosine digital signals orthogonal to each other;
• and
• wherein the pre-distortion filter is connected to the baseband generation unit for pre-distortion of the baseband signal, and is loaded in real time with the automatically generated h-factor;
• and
• wherein the data switch is connected to the pre-distortion filter for switching the calibration signal and the baseband signal into the digital-to-analog conversion module;
• (2) determining that vector signal generator path state parameters are set to change, and setting whether the automatic calibration is carried out by the parameters, if yes, enter a calibration mode and continue to step (3);
• otherwise, enter the working mode and exit the step;
• (3) obtaining frequency response measurements over an entire baseband bandwidth by varying a signal output frequency of the calibration signal generator based on a baseband sampling rate and the order of the pre-distortion filter as a frequency step;
• (4) automatically calculating in real time a set of filter coefficients h(n) for the conversion generation pre-distortion filter with the pre-distortion filter connected to the baseband generation unit;
• and
• (5) automatically loading in real time the set of filter coefficients h(n) into the pre-distortion filter to complete a frequency response amplitude correction over the entire modulation bandwidth.